﻿using System; 
using System.Linq;
using System.Collections.Generic;
using System.Text;
using System.ComponentModel; 
using System.Linq.Expressions;
using System.Collections; 
using System.Reflection; 
using System.Xml.Linq;
 
namespace System.Data.Linq
{
    /// <summary>
    /// Adds sorting feature to BindingList<T> 
    /// </summary>
    /// <typeparam name="T"></typeparam> 
    internal class SortableBindingList<T> : BindingList<T> { 
        internal SortableBindingList(IList<T> list) : base(list) { }
 
        private bool isSorted = false;
        private PropertyDescriptor sortProperty = null;
        private ListSortDirection sortDirection = ListSortDirection.Ascending;
 
        protected override void RemoveSortCore() {
            isSorted = false; 
            sortProperty = null; 
        }
 
        protected override ListSortDirection SortDirectionCore {
            get { return sortDirection; }
        }
        protected override PropertyDescriptor SortPropertyCore { 
            get { return sortProperty; }
        } 
        protected override bool IsSortedCore { 
            get { return isSorted; }
        } 
        protected override bool SupportsSortingCore {
            get { return true; }
        }
 
        protected override void ApplySortCore(PropertyDescriptor prop, ListSortDirection direction) {
            //Only apply sort if the column is sortable, decision was made not to throw in this case. 
            //Don't prevent nullable types from working. 
            Type propertyType = prop.PropertyType;
 
            if (PropertyComparer.IsAllowable(propertyType))
            {
                ((List<T>)this.Items).Sort(new PropertyComparer(prop, direction));
                sortDirection = direction; 
                sortProperty = prop;
                isSorted = true; 
                OnListChanged(new ListChangedEventArgs(ListChangedType.Reset, -1)); 
            }
        } 

        internal class PropertyComparer : Comparer<T> {
            private PropertyDescriptor prop;
            private IComparer comparer; 
            private ListSortDirection direction;
            private bool useToString; 
 
            internal PropertyComparer(PropertyDescriptor prop, ListSortDirection direction) {
                if (prop.ComponentType != typeof(T)) { 
                    throw new MissingMemberException(typeof(T).Name, prop.Name);
                }
                this.prop = prop;
                this.direction = direction; 

                if (OkWithIComparable(prop.PropertyType)) { 
                    Type comparerType = typeof(Comparer<>).MakeGenericType(prop.PropertyType); 
                    PropertyInfo defaultComparer = comparerType.GetProperty("Default");
                    comparer = (IComparer)defaultComparer.GetValue(null, null); 
                    useToString = false;
                }
                else if (OkWithToString(prop.PropertyType)) {
                    comparer = StringComparer.CurrentCultureIgnoreCase; 
                    useToString = true;
                } 
            } 

            public override int Compare(T x, T y) { 
                object xValue = prop.GetValue(x);
                object yValue = prop.GetValue(y);

                if (useToString) { 
                    xValue = xValue != null ? xValue.ToString() : null;
                    yValue = yValue != null ? yValue.ToString() : null; 
                } 

                if (direction == ListSortDirection.Ascending) { 
                    return comparer.Compare(xValue, yValue);
                }
                else {
                    return comparer.Compare(yValue, xValue); 
                }
            } 
 
            protected static bool OkWithToString(Type t) {
                // this is the list of types that behave specially for the purpose of 
                // sorting. if we have a property of this type, and it does not implement
                // IComparable, then this class will sort the properties according to the
                // ToString() method.
 
                // In the case of an XNode, the ToString() returns the
                // XML, which is what we care about. 
                return (t.Equals(typeof(XNode)) || t.IsSubclassOf(typeof(XNode))); 

            } 

            protected static bool OkWithIComparable(Type t) {
                return (t.GetInterface("IComparable") != null)
                    || (t.IsGenericType && t.GetGenericTypeDefinition() == typeof(Nullable<>)); 
            }
 
            public static bool IsAllowable(Type t) { 
                return OkWithToString(t) || OkWithIComparable(t);
            } 
        }
    }
}

// File provided for Reference Use Only by Microsoft Corporation (c) 2007.
// Copyright (c) Microsoft Corporation. All rights reserved.